[1] It is observed on the anniversary of the March 25, 1634, landing of the first European settlers in the Province of Maryland, the third English colony to be settled in British North America.

Three Jesuit priests were collected from Cowes on the Isle of Wight in England where they avoided having to give the oath of allegiance and supremacy to the King.

In thanksgiving for the safe landing, Jesuit Father Andrew White celebrated the Mass for the colonists led by the younger brother of Lord Baltimore, Leonard Calvert, (1606-1647), who served as the first governor, and perhaps for the first time ever in this part of the world on the first landing at Blackistone Island, later known as St. Clement's Island off the northern shore of the Potomac River, which was the new border between the new colony and the earlier English settlements in Virginia) and erected a large cross.

The landing coincided with the Feast of the Annunciation, a holy day honoring Mary, and the start of the new year in England's legal calendar (prior to 1752).

Later the colonists and their two ships sailed further back down river to the southeast to settle a capital at St. Mary's City near the point where the Potomac flows into the Chesapeake Bay.